Articles | Volume 3, issue 2
Clim. Past, 3, 225–236, 2007
Clim. Past, 3, 225–236, 2007

  22 May 2007

22 May 2007

Spatial structure of the 8200 cal yr BP event in northern Europe

H. Seppä1, H. J. B. Birks2,3,4, T. Giesecke5, D. Hammarlund6, T. Alenius7, K. Antonsson8, A. E. Bjune2,3, M. Heikkilä1, G. M. MacDonald9, A. E. K. Ojala7, R. J. Telford2,3, and S. Veski10 H. Seppä et al.
  • 1Department of Geology, University of Helsinki, P.O. Box 64, 00014, Finland
  • 2Department of Biology, University of Bergen, Allégaten 55, 5007 Bergen, Norway
  • 3Bjerknes Centre for Climate Research, Allégaten 55, 5007 Bergen, Norway
  • 4Environmental Change Research Centre, University College London, 26 Bedford Way, London, WC1H OAP, UK
  • 5Department of Geography, University of Liverpool, Roxby Building, Liverpool, L69 7ZT, UK
  • 6GeoBiosphere Science Centre, Quaternary Sciences, Lund University, Sölvegatan 12, 22362 Lund, Sweden
  • 7Geological Survey of Finland, P.O. Box 96, 02151 Espoo, Finland
  • 8Department of Earth Sciences, Uppsala University, Villavägen 16, 75236 Uppsala, Sweden
  • 9Department of Geography, UCLA, 405 Hilgard Avenue, Los Angeles, CA 90095-1524, USA
  • 10Institute of Geology, Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn, Estonia

Abstract. A synthesis of well-dated high-resolution pollen records suggests a spatial structure in the 8200 cal yr BP event in northern Europe. The temperate, thermophilous tree taxa, especially Corylus, Ulmus, and Alnus, decline abruptly between 8300 and 8000 cal yr BP at most sites located south of 61° N, whereas there is no clear change in pollen values at the sites located in the North-European tree-line region. Pollen-based quantitative temperature reconstructions and several other, independent palaeoclimate proxies, such as lacustrine oxygen-isotope records, reflect the same pattern, with no detectable cooling in the sub-arctic region. The observed patterns challenges the general view of the wide-spread occurrence of the 8200 cal yr BP event in the North Atlantic region. An alternative explanation is that the cooling during the 8200 cal yr BP event took place mostly during the winter and spring, and the ecosystems in the south responded sensitively to the cooling during the onset of the growing season. In contrast, in the sub-arctic area, where the vegetation was still dormant and lakes ice-covered, the cold event is not reflected in pollen-based or lake-sediment-based records.